Pressure sensitive record material



TBS

can

National Cash Register Company, Dayton,

Ohio, a corporation of Maryland No Drawing. Application November 8,1947, Serial No. 784,938

28 Claims.

It This invention relates to improvements in pressure-sensitive recordinaterialv This application is a continuation in part of the pendingapplications of Barrett H. Green, Serial No. 520,573, filed January 31,1944, for Record material and coating for same, now abandoned; SerialNo. 581,334, filed March 9, 1945, for Coat ing for record material, nowabandoned; and Serial No. 601,761, filed June 2'7, 1945, for Method ofmaking pressure sensitive marking coatings for record material, nowabandoned, as a division of said co-pending application Serial No.581,834.

The principal object of this invention is to provide apressure-sensitive record material on which a mark of distinctive colormay be produced by the mere application of localized pressure and whichis not subjectto the disadvantages inherent in the pressure sensitiverecordmater ial disclosed in United States Letters Patent No. 2,299,693,patented October 20, 1942, on the a p plication filed by Barrett K.Green on February 23, 1940, That patent discloses a pressure-sensitiverecord material including the combination of an insulating medium, arupturable solid material such as gum dammar, having included thereininterspersed droplets of a plurality of liquid reagents, which arechemically reactive to produce a distinctive color in the recordmaterialat the points of application of localized pressure lereto, such pressurerupturing the insulating medium to permit chemical reaction between thetwo liquid reagents. The two reagents disclosed in this patent aregallic acid and ferric ammonium sulphate, each dissolved in glycerine.These reagents are ionized by the glycerine, which constitutes anionizing medium, and the chemical reaction proceeds by interchange ofions when the two solutions are allowedto mix, upon the rupture of theinsulating medium. The reaction disclosed in that patent depends uponthe presence of the reagents in an ionizing medium. However, anyavailable ionizing medium is hygroscopic, with the result that therecord material made in accordance with this patentis sensitive to anexcess of moisture, and conditions of high humidity may cause theinsulating me dium to cease to be effective, with the result that thechemical reaction takes place without any application of localizedpressure, and-the record material is stained and discolored, so that itceases to be useful.

As stated above, the principal 2 object of the V present invention is toprovide a pressure-sensitive record material that is not subject to thedefects and disadvantages of that disclosed in Patent No. 2,299,693, asindicatedabove.

Another object or the present invention is to provide a "record materialupon which a mark of distinctive color may be produced, at the points ofapplication of localized pressure thereto, by such mere application oflocalized pressure, and which willnot become discolored or stained dueto the effect or light, atmospheric conditions, or i In short, it is theobject of this invention to provide a pressuresensitive record materialin which the marker distinctive color will be produced only'at thepoints of application of localized pressure, and at no other points, andunder no other conditions.

Another object or this invention is to provide a pressure-sensitiverecord material inwhich the mark of distinctive color is produced by thechemical reaction of color forming reactants, in the absence of anyliquid ionizing medium there for.

A further object or this invention is to provide a pressure-sensitiverecord material in which a mark of distinctive color is produced by a reaction between solid particles of color-forming reactants. 7

Further objects, and objects relating to details and economies ofproduction, will definitely ap pear from the detailed description tofollow. Theobjects of this invention have been attained by the severalembodiments thereof described in detail in the following specification.This invention is clearlydefined and pointed out in the appended claims.

In general, the present invention contemplates a pressure-sensitiverecord material comprising, in combination, a plurality of adsorpticncolorforming reactants, such reactants being so selected-that theyreact, in the absence of a liquid ionizing medium for the reactants, toform a distinctive color when brought into adsorption contact with eachother, and a solid insulating medium insulating said reactants fromcolorforming reaction contact with each other. Upon application oflocalized pressure to the'record material, as by drawings. stylus acrossit, the insulating medium is ruptured at the points' of application ofsaid localized pressure, and such rupture permits co1or=forming reactioncontact 3 between the reactants at such points, in the absence of anyliquid ionizing medium for said reactants. The result is that a mark ofdistinctive color is produced by the mere application of localizedpressure.

In the preferred form of this invention, both of the color-formingreactants, as well as the insulating medium, are in the solid state, andthe color-forming reaction takes place upon mere contact of solidparticles of the reactants. A pressure-sensitive record material may beprovided in which the solid particles of a plurality of color-formingreactants are interspersed in a solid insulating medium, which insulatesthe particles from color-forming reaction contact with each other. Therupture of this solid insulating medium by the application of localizedpressure permits the soLd particles of colorforming reactants to reactwith each other, at the points of application of such pressure, toproduce the mark of distinctive color. According to one form of thisinvention, solid particles of one of the color-forming reactants arecarried by and dispersed in a, solid insulating medium, to which acoating of solid particles of another color-forming reactant is applied.In this case, the application of localized pressure ruptures the solidinsulating medium at the points of application of such pressure andbrings about color-forming reaction contact between the solid particlesof color-forming reactants at such points, thus producing the mark ofdistinctive color. Preferably, this pressure-sensitive record materialincludes a supporting member, such as a fibrous web of paper or thelike, to which the coating of solid insulating medium and thecolor-forming reactants is applied.

Since it is diificult to show precisely the spatial relationship betweenthe solid particles of colorforming reactants, the solid insulatingmedium,

Of the reactant materials employed the organic material is an electrondonor aromatic compound having a double bond system which is convertibleto a more highly polarized conjugated form upon taking part in anelectron acceptor-donor solid surface chemical reaction, giving it adistinctive color, and the inorganic material is a material which actsas an acid relative to the organic material so as to be an electronacceptor when in adsorption contact therewith. Both materials are infine particle form in order to furnish a large reactant surface area perunit area of the record material which enhances the depth of color perunit area of the record material.

In the following examples, there will be described embodiments of thisinvention, by means of which the objects of the invention have beensuccessfully attained.

The following embodiment of this invention constitutes the best mode ofapplying the principle thereof contemplated up to the present time andmay be considered the preferred embodiment. It comprises a base web ofpaper or the like, to which is applied a coating including casein andsolid particles of three color-forming reactants; namely, kaolin, thecompound 3,3 bis (p-dimethylaminophenyl) -6 dimethylamino phthalide,

referred to as crystal violet lactone and having the structure and thecompound tetramethylbenzidine, having the structure The caseinconstitutes the solid insulating medium, insulating one of thecolor-forming reactants-that is, kaolin-from color-forming re actioncontact with the other color-forming reactantsthat is, crystal violetlactone and tetramethylbenzidine. This record material is normally whiteor bluish white in color, and, upon the application of localizedpressure thereto, as by drawing a stylus thereover, a dark blue mark isproduced at the points of application of such localized pressure. Suchapplication of pressure ruptures the solid insulating medium at thepoints of application of pressure, permitting color-forming reactioncontact between the solid particles of kaolin and the solid particles ofcrystal violet lactone and tetramethylbenzidine, thus causing the colorchange at such points that produces the mark.

The compound 3,3 bis (p-dimethylaminophenyl) 6 dimethylaminophtha1ide-that is, crystal violet lactone-and the process of making itare disclosed in United States Letters Patent No. 2,417,897, issuedMarch 25, 1947, on the application of Clyde S. Adams, filed June 16,1945, although the compound is incorrectly named in said patent as 3,3bis (4-dimethylaminophenyl) 6 dimethylaminophenyl phthalide.

It is not considered that the proportions in which these severalingredients are present in the record material are of particularimportance, but good results have been obtained with apressure-sensitive record material having such ingredients present inthe following proportions by Weight in the coating on the base web:

Per cent Casein 8.85 Kaolin 88.50 Crystal violet lactone 2.25Tetramethylbenzidine .40

When these ingredients are applied to the paper as a coating thereon,such coating weighs about .0023 pound per square foot of surface and mayhave a thickness of the order of from .0005 to .001 inch. The thicknessof the coating varies, of course, with the treatment to which the recordmaterial is subjected in finishing. The solid particles of kaolin inthis record material may be of about the order of ten microns indiameter, although considerable variation in particle size is possiblewithout any ill eflects. Particle size of the crystal violet lactone andthe tetramethylbenzidlne is largely determined by the method ofapplication of those ingredients. The particles of these reactants maybe as large as ten microns in diameter and frequently are much smaller.

@rgauic nlm forming hydrophilic colloid substances such asgelatinamethyl cellulose, starch, polyvinyl alcohol, and animal glue arerepresentative materials that may be substituted for casein as the solidinsulating medium. Any of the following inorganic materials may besubstituted for kaolin as one of the color-forming reactants:attapulgite (Attapulgus clay), pyrophyllite, talc, bentonite,halloysite, calcium sulphate, calcium citrate, magnesium trisilicate,aine sulphide, zirconium dioxide, calcium phosphate, barium sulphate,and calcium fluoride. When a y of these materials are substituted forthe kaolin in this combination, the resulting record material will bewhite or bluish white in color, and a dark blue mark will appear thereonas the result of the application of localized pres.- u e- If thetetramethylbenzidine be omitted and the pressure-sensitiye recordmaterial be made using kaolin and crystal violet lactone as the solecolorforming reactants, the record material will be white in. color, andapplication of localized pres sure will produce a dark blue markthereon, but this mark may fade upon continued exposure to light underconditions of high humidit On the other hand, if the crystal violetiactone be omitted and tetramethylbenzidine kaolin be user. the solecolor-forming reactants, pressuresensitive record material produced willbe normally white, and application of localized pressure theretowillproduce a green mark, which deepens in color upon aging and does notfade as readily, under conditions of high humidity, as the mark producedby crystal violet lactone and kaolin alone.

This pressure-sensitive record material is not substantially affected bythe amount of atmospheric humidity ordinarily encountered, although themay fade somewhat if subjected to high humidity for a long-continuedperiod of time. However, this pressure-sensitive record material doesnot become stained or discolored by exposure to high humidity for longperiods of time and retains its ability to respond to the application oflocalized pressure and to produce the mark of dis-. tinctive color undersuch conditions. This is thought to be due to the fact that the recordmaterial does not include any hygroscopic ionizing media. Consequently,the structure of the record material is not altered or modified due tothe absorption of water from the atmosphere.

One method that has been used successfully to make thepressure-sensitive record material described above is as follows: Aslurry of kaolin and water was prepared including fifty parts by weightof kaolin to fifty parts by weight of water, and a small amount of asuitable dispersing agent, such as sodium metaphosphate, for instance,in the proportion of 0.075% by weight was added to facilitate thedispersion of the particles of kaolin throughout the slurry. Theaddition-of this dispersing agent reducesthe viscosity of the slurryconsiderably, thusfacilitating its mixing and application and alsopreventing the settling of the solid particles of kaolin. A by weightsolution of casein in water was formed by, first, disparsing the caseinin cold water by stirring for fifteen minutes at room temperature and,then, heating up to 60 degrees centigrade. Five parts by weight of a 28%ammonium hydroxide solutionthat is, one having a specific gravity of25.9" .3 a

w r th ddediothe hwcaseinsclu ou. w ich i r o ab u fi teen minute anda oed to .cool to room temperature. The kaolin urry and the alkaline caseinsolution were then firoughly mi' ed and blen ed h i of ten pa t by i hof kaoli t o e vpart o c n. and, at this stage, a small percentage-Jarinstance, about 0.05% .by -weight. o f:tributyl phos-.- phat .inalcohol, or other antisfoaming agent, was added. This mixture of thekaolin slurry and the casein solution was then applied as a coatingtothe paper, and-the coated paper was dried and oalendered-or'treated inany desired way to give the proper surface finish. A solution in tolueneor about 2.55% by weight of crystal yiolet lactotoe and about .i 5% bweight of tetramethylbenzidine was then applied to the coated side ofthe paper, the excess or" this solution was removed in any suitable way,as bypassing under a doctor blade, and then the treated paper was. driedto evaporate the toluene and was ready for use.

A successful pressure-sensitive record material as that described above,using casein as the solid insulating medium and kaolin, crystal violetlactone, and tetrame-thylbenzidine as the color.- f-orming reactants,was,- made by the following process: 206 grams of kaolin were made intoaslurry with 200 gramsofwater, to which 0.3% by weight of sodiummetaphosphate was added as a dispersing agent. A case-in solution wasformed dispersing 20 grams of casein in 139 grams of cold water andstirring for fifteen minutes. This dispersion of casein in water wasthen heated to 60 degrees Centigrade, andi grams of commercial 28%ammonium hydroxide solution were added, and the solution was stirred forfifteen minutes while hot, after which it was allowed to cool to roomtemperature. One-half of the casein sol-irtion thus formed wasthoroughly mixed with the kaolin slurry. 5.1 grams of crystal violetlactone and .9 gram of tetramethylbenzidine were then dissolved in 50cc. of 3.7% hydrochloric acid solution having aspecific gravity of 25Be. at

To the other halfofthe casein solution, 5 grams of commercial 26%ammonium hydroxide solution were added, and the acidified solution ofcrystal. violet lactone and tetramethylbenzidine was added slowly tothis portion of the casein solution, with continued stirring, for aboutan hour. The portion of the casein solution containing the kaolin waspassed through a homogenizer or other means for mixing and thoroughlydispersing the particles of kaolin in the casein solution, and the twoportions of casein solution, one containing the kaolin and the othercontaining the crystal violet lactone and the tetramethylbenzidine, werethen mixed thoroughly and applied as a coating to the base web of paper.This coating was then dried on the paper in the usual manner. Theresulting record material had a light bluish white color approachingwhite.

t shouldbe noted that the mixing of the ammoniacal kaolin-containingportion of the casein solution with the other portion of the caseinsolution, containing the crystal violet lactoneand thetetramethylbenzidine,results in an alkaline mixture, in which thecrystal violet lactone and the tetramethylbenzidine are precipitated inextremely fine particles.

In case gelatinissubstituted for casein as the oli i s g m dium. theprocedure described;

above is modified, in that the gelatin is first dis-'- solved in waterat a temperature above 40 degrees 'centigrade, and this gelatin solutionis then divided into two equal parts, to one of which the slurry ofkaolin and water is added as before. The other part of the gelatinsolution is made sufiiciently ammoniacal to neutralize and precipitatethe crystal violet lactone and the tetramethylbenzidine when thehydrochloric acid solution of these ingredients is added thereto. Thesetwo portions of the gelatin solution are then mixed, and the mixture isapplied as a coating to the paper and then dried. It should be notedthat, when gelatin is used as the solid insulating medium, the gelatinsolution should be kept at a temperature above 40 degrees centigradethroughout the entire procedure.

In case methyl cellulose is used as the solid insulating medium insubstitution for the casein,

a solution is prepared by dissolving about parts by weight of methylcellulose (of any viscosity between 2006 and 4000 centipoises at 68degrees Fahrenheit) in about 50 parts by weight of water, and thissolution is divided into two equal parts. To one portion of the methylcellulose solution, the slurry of kaolin and water is added, in theratio of 40 parts by weight of kaolin to one part by weight of methylcellulose, and mixed, as described in connection with the use of casein.The other portion of the methyl cellulose solution is renderedsufficiently ammoniacal to precipitate the crystal violet lactone andthe tetramethylbenzidine from the hydrochloric acid solution thereof,when the latter is added to and mixed with this portion of the methylcellulose solution in such proportions that the ratio by weight ofkaolin to crystal violet lactone and tetramethylbenzidine in the coatingwill be 100 to 3. The two portions of the methyl cellulose solution arethen thoroughly mixed and applied as a coating to the paper, whichcoating is dried.

Another embodiment of this invention comprises a base web of paper orthe like having applied thereto a coating including casein or methylcellulose as the solid insulating medium and solid particles of twocolor-forming reactants; namely, kaolin and the compound 3,3 bis(p-dimethylaminophenyl) phthalide, also known as malachite greenlactone, having the structure This record material is normally white orlight in color, and, upon application of localized pressure thereto, asby drawing a stylus thereover, a mark of dark blue-green color isproduced at the points of application of such pressure.

Record material made with malachite green lactone is claimed in adivisional application, Serial No. 59,422, filed November 10, 1948.

Another embodiment of this invention comprises a base web of aper havingapplied thereto a coating including casein as the solid insulatingmediumand two color-forming reactants; name- 1y, kaolin and the compound2,4 bis [p- (p-dimeth- P3 it v ylaminophenylazo) anilinolG-hydroxy sym.triazine, having the structure The pressure-sensitive record materialmade using these ingredients is normally yellow in color, and theapplication of localized pressure thereto, as by drawing a stylus acrossthe material, ruptures the solid insulating medium and permits the solidparticles of kaolin and the o r ganic color-forming reactant to comeinto colorforming reaction contact with each other, producing a darkblue mark at the points of application of such localized pressure.

Record material made with the above identified triazine compound isclaimed in a divisional application, Serial No. 59,423, filed November10, 1943.

Another embodiment of this invention consists of a pressure-sensitiverecord material including a base web of paper having applied thereto acoating including casein as the solid insulating medium and twocolor-forming reactants; namely, kaolin and the compound o-hydroxybenzalacetophenone, having the structure.

This record material comprise solid particles of kaolin ando-hydroxybenzalacetophenone insulated from color-forming reactioncontact with each other by casein as the solid insulating medium. Therecord material is normally light yellow in color, and application oflocalized pressure thereto ruptures the insulating medium at the pointsof application of such pressure, per mitting color-forming reactioncontact between the particles at such points and producing areddish-yellow mark.

Record material made with o-hydroxy-benzalacetophenone is claimed in adivisional application, Serial No. 59,424, filed November 10, 1948.

Another pressure-sensitive record material constituting an embodiment ofthis invention that has been successfully made consists of a web ofpaper having applied thereto a coating comprising casein as the solidinsulating medium and two color-forming reactants; namely, kaolin andthe compound bis (p-dimethylaminophenyl) methanol, also known asMichlers hydrol and having the structure Record material made withMichlers hydrol is normally white or light gray but produces a dark bluemark at points of marking pressure.

Another embodiment of this invention consists of a web of paper havinapplied thereto a coating comprising casein as the solid insulatingmedium and two color-forming reactants; namely, kaolin and the compoundbis (p-dimethylaminophenyl) methoxy methane. also known as methyletherof Michlershydrol, having the structural formula Record materialmade with themethyl ether of Michlers hydrol is normally white orgrayish and produces a dark blue mark at points of marking pressure.

Record material made with Michlers hydrol or the methyl ether ofMichlers hydrol is claimed in a divisional application, Serial No.59,425, filed November 10, 1948.

Another record material constituting an embodiment of this inventionconsists of a Web of paper having applied thereto a coatingcomprisingcasein as the solid insulating medium andi i two color-formingreactants; namely, kaolin and the compound 3,3 his(p-diethylaminophenyl) phthalide, having the structural formula Recordmaterialma de with 3,3 bis (p-diethylaminophenyl) phthalide is normallywhite and produces a blue green mark at points of marking pressure. Itis claimed with record material made with 3,3 bis (p-di-npropylaminophenyl) phthalide in a divisional application, Serial No. 1

59,426, filed November 10, 1948.

Another embodiment ,"Of 2 this invention consists of thepressure-sensitive record material comprising'a web oizpaper havingapplied thereto a coating including casein, as the'solid insulatingmedium and solid particles of two colorforming reactants; namely, kaolinand the compound 3,3 bis (p-methylaminophenyl) phthalide, having thestructural formula This record material is normally white, but

the application of. localized pressure thereto-ruptures the insulatingmedium, casein, at [thepoints of application of such pressure,permitting colorforming reaction contact between; the solid particles ofkaolin and the solid particles of the compound '3,3 his,(pem'ethylaminophenyll phthalide, resulting .in the prodncticnof .abright 'blueimark.

Record :material made with bis (p-methylaminophenyl) phthalide is.ciaimedwith, record material made with 3,3 bis (p-ethylaminophenyl)phthalide in divisional application, SerialNo.

59,427, filed Novembcrilii, 1948.

Another embodiment of this invention is a pressureesensitive,:record:material: consisting of a web :of paper havingiappliedthereto a coating.ih consisting of caseinas the -.so1i'd insulating medium and solidparticles .of two color-forming reactants; namely, kaolinandthe compound3,3

bis (p-ethylaminophenyl) phthalide, havingcthe structural formula (C215) HN-- I ,NHUJIHB) This record material is normally white,"but theapplication of localized pressure thereto ruptures the solid insulatingmedium at the points of application of such pressure, thus permittingcolor-forming reaction contact between the solid particles of kaolin and3,3 bis (p-ethylaminophenyl) phthalide, resulting in a bright blue mark.

Another embodiment of this invention is a pressure-sensitive recordmaterial consisting of a Web of paper having applied thereto a coatingincluding casein as the solid insulating medium and solid particles oftwo color-forming reactants; namely, kaolin and the compound 2(4,4'

his dimethylaminobenzohydryl) 5 dimethylaminobenzoic acid, having thestructural 'formula:

omen- ,l l'tCHs): The record-material is normally white, and

the application ofloca-lized :pressure thereto ruppoundgfi bis (p-di npr pylaminophenyl) phthaiide; having, the structural formula:

(aims This record material is normally whitanan Tie -the .solidinsulating medium, casein, insulates the solid particles of kaolin fromcolor-forming reaction contact with the solid particles of the compound3,3 bis (pi-di n-propylaminophenyl) -phthalide, but the application oflocalized pressure to this record material ruptures the insulatingmedium and permits color-forming reaction contact between the solidparticles or" the two reactants, thus producing a blue-green mark at thepoints of application of such pressure.

Another pressure-sensitive record material constituting an embodiment ofthis invention consists of a web of paper having applied thereto acoating including casein as the solid insulating medium and solidparticles of two color-forming reactants, kaolin and the compound 3,3bis l-dimethylamino S-methyl phenyl) phthalide, having the structuralformula:

This record material is normally white, but a blue mark is producedthereon by the application of localized pressure, which ruptures theinsulating medium, casein, and permits colorforming reaction contactbetween the solid particles of the reactants at the points ofapplication of such localized pressure.

Record material made with 3,3, bis i-dimethylamino 3-methylaminopheny1)phthalide is claimed in a divisional application, Serial No. 59,429,filed November 10, 1948.

Another pressure-sensitive record material constituting an embodiment ofthis invention consists of a web of paper having applied thereto acoating including casein as the solid insulating medium and solidparticles of two color-forming reactants; namely, kaolin and thecompound 4' (p-dimethylaminophenylazo) benzanilide, having thestructural formula:

HO III This record material is normally light yellow in color, but theapplication of localized pressure thereto produces a dark brown markthereon at the points of application of such pressure.

Record material made with the benzanilide compound is claimed in adivisional application, Serial No. 59,430, filed November 10, 1948.

The methods and processes of making pressure-sensitive record materialdisclosed herein are not claimed in this application but are disclosedand claimed in the pending application of Barrett K. Green, Serial No.784 939, filed November 8, 1947, for Process for makingpressuresensitive record material.

It is understood that the pressure-sensitive record material describedherein is susceptible of particles of a plurality of adsorbentcolor-forming reactants deposited in contiguity to each other on saidmember; and a solid insulating medium including an organic hydrophilicfilm-forming material inert as to and insulating said solid reactantparticles from color-forming reaction contact with each other, a firstone of said reactants being solid particles of an electron donoraromatic organic compound having a double bond system which isconvertible to a more highly polarized conjugated form upon taking partin an electron acceptor-donor solid surface chemical reaction, giving ita distinctive color, and a second of said reactants being solidinorganic material in fine particle form providing a large adsorbentsurface area and which is an acid relative to the first reactant so asto be an electron acceptor when in adsorption contact with said firstreactant, and said reactants being adsorbable one upon the other, theinsulating medium being of such texture that application of localizedpressure to the record material ruptures said insulating medium at thepoints of application of such pressure to permit adsorptioncolor-forming reaction contact of the solid reactant particles at suchpoints, whereby a mark of distinctive color is produced by mereapplication of localized pres sure.

2. The record material of claim 1 in which the first one of thecolor-forming reactants is the compound 3,3 bis(p-dimethylaminophenyl)-6 dimethylamino phthalide, having the structure3. The record material of claim 2 in which the second color-formingreactant is kaolin.

4.. The record material of claim 3 in which the solid insulating mediumis casein.

5. The record material of claim 1 in which the 'first one of thecolor-forming reactants is the compound 3,3 bis (p-dimethylaminophenyl)-6 dimethylamino phthalide, having the structure (0 Ha) aN- N (0 H3) 1 Uah mixed with tetramethylbenzidine, having the structure (onomGG-moam 6.The record material of claim 5 in which the second color-formingreactant is kaolin.

7. The record material of claim 1 in which the second one of thecolor-forming reactants is kaolin.

8. The record material of claim 1 in which the solid insulating mediumis casein.

9. Pressure-sensitive record material including the combination of asupporting member; a solid pressure-rupturable medium derived from anoraaodeacgarlic hydrophilic colloid film-forming material; solidparticles of a first color-forming reactant dispersed therein and solidparticles of a second color-forming reactant deposited thereon, the saidparticles of the second reactant being an electron donor aromaticorganic compound having a double bond system which is convertible to amore highly polarized conjugated form upon taking part in an electronacceptor-donor solid surface chemical reaction giving it a distinctivecolor and the first of said color-forming reactants being solidinorganic material in fine particle form providing a large adsorbentsurface area and which is an acid relative to the second reactant so asto be an electron acceptor when in adsorption contact with said secondreactant, and said reactants being adsorbable one upon the other, saidsolid insulating medium normally insulating said first and second solidreactant particles from color-forming reaction contact with each other,the application of localized pressure to the record material rupturingsaid insulating medium at the points of application of such pressure topermit color-forming reaction contact of the solid reactant particles atsuch points, whereby a mark of distinctive colorisproduced by mereapplication of localizedpressure.

10. The record material of claim 9 in which the second color-formingreactant is the compound 3,3 bis (p-dimethylaminophenyl')'--6dimethylamino phthalide,. having the. structure 11. The record materialof claim 10 in which the first color-forming reactant is kaolin.

12. The record material of claim 11 in which the solid insulating mediumis casein.

13. The record material of claim 9 in which the second color-formingreactant is a mixture of the compound 3,3 bis (p-dimethylamincphenyl) 6dimethylamino phthalide, having the structure U a): and the compoundstetramethylbenzidine, having the structure from an organic hydrophiliccolloid film-forming material; and solid particles of a plurality ofcolor-forming reactants interpersed in said solid medium and insulatedthereby from color-forming reaction contact with each other, a first oneof said reactants being solid particles of an electron donor aromaticorganic compound having a double bond system which is convertible toamore higherpolarized conjugated form-upon taking part in. anelectronacceptor-donor solid surface chemical reaction, giving it a distinctivecolor, and a second of said reactants being solid inorganic material infine particle form providing a large adsorbent surface area and which isan acid relative to the first reactant so as to be an electron acceptorwhen in adsorption contact with said first reactant, and said reactantsbeing adsorbable one upon the other, the application ofidealized-marking pressure to the record material rupturing saidinsulating medium at the points of application of pressure to permitcolor-forming reaction contact of the solid reactant particles at suchpoints, whereby a mark of distinctive color is produced by mereapplication of localized .f pressure;

17. The record material of claim 16 in which the first one of thecolor-forming reactants is the compound 33' bis (p-dimethylarnihophenyl)6 dimethylamino phthalide, having the structure 18. The record materialof claim 17 in which the second color-forming reactant is kaolin;

19-. The record material of claim 18 in which the solid insulatingmedium is casein.

20. The record material of claim 16 in which the first color-formingreactant includes the compound 3,3 bis (p-dimethylaminophenyl) -6dimethylamino phthalide, having the structure and the compoundtetramethylbenzidine, having the structure (OHahNQON (cm):

21. The record material of claim 20 in which the second of thecolor-forming reactants is kaolin.

22. The record material of claim 21 in which the solid insulating mediumis casein.

23. Pressure-sensitive record material including the combination of abase web and a coating thereon, said coating including solid particlesof a plurality of color-"forming reactants, so selected as to act in theabsence of an ionizing medium to aqose tact with each other; anddisposed in proximity to each other, and a solid-insulating mediumderived from a hydrophilic colloid film-forming material insulating saidreactants from color-forming reaction contact with each other, -a firstone of said reactants being solid particles of an electron donoraromatic organic compound having a double bond system which isconvertible to a more highly polarized conjugated form upon taking partin an electron acceptor-donor solid surface chemical reaction, giving ita distinctive color, and a second of said reactants being solidincrganic material in fine particle form providing a large adsorbentsurface area and which is an acid relative to the first reactant so asto be an electron acceptor when in adsorption contact with said firstreactant, and said reactants being adsorbable one upon the other, theapplication of localized pressure to the record material rupturing saidinsulating medium at the points of application of such pressure topermit color-forming reactioncontact between the reactants at suchpoints, whereby a mark of distinctive color is produced by mereapplication of localized pres sure.

24. The record material of claim 23 in which the first one of thecolor-forming reactants is the compound 3,3 bis(p-dimethylaminophenyl)-6 dimethylamino phthalide, having the structure25. The record material of claim 24 in which the second color-formingreactant is kaolin.

16 26. The record material of claim 25 in which the solid insulatingmedium is casein.

27. The record material of claim 23 in which the first one of thecolor-forming reactants is the compound 3,3 bis (p-dimethylaminophenyl)-6 di? methylamino phthalide, having the structure mixed withtetramethylbenzidine, having the structure (GHQQN-O-Q-NKJHQ:

28. The record material of claim 27 in which the second color-formingreactant is kaolin.

BARRETT K. GREEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,083,206 Schoeller June 8, 19372,299,693 Green Oct. 20, 1942 FOREIGN PATENTS Number Country Date550,332 Great Britain Jan. 4, 1943 OTHER REFERENCES Hauser et al.:Journal American Chem. 500., July 1940, vol. 62, pages 1811 to 1814.

Certificate of Correction Patent No. 2,505,470 April 25, 1950 BARRETT K.GREEN It is hereby certified that errors appear in the printedspecification of the above numbered patent requiring correction asfollows:

Column 8, l'me 1, sym should be italicized; column 11, line 3, for pi-diread p-d'i; column 13, line 64, for compounds read compound;

and that the said Letters Patent should be read with. these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 8th day of August, D. 1950.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents.

